Re: [Xen-devel] [PATCH v7 1/3] x86/tlb: introduce a flush HVM ASIDs flag

From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Julien Grall <julien@xen.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	Tim Deegan <tim@xen.org>, Jan Beulich <jbeulich@suse.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [PATCH v7 1/3] x86/tlb: introduce a flush HVM ASIDs flag
Date: Thu, 19 Mar 2020 18:38:25 +0100	[thread overview]
Message-ID: <20200319173825.GQ24458@Air-de-Roger.citrite.net> (raw)
In-Reply-To: <83b8dc44-6ecf-9bdf-957b-3c502e4df926@xen.org>

On Thu, Mar 19, 2020 at 04:21:23PM +0000, Julien Grall wrote:
> Hi,
> 
> On 19/03/2020 15:47, Roger Pau Monne wrote:
> > diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
> > index d0d095d9c7..02aad43042 100644
> > --- a/xen/include/xen/mm.h
> > +++ b/xen/include/xen/mm.h
> > @@ -644,7 +644,7 @@ static inline void filtered_flush_tlb_mask(uint32_t tlbflush_timestamp)
> >       if ( !cpumask_empty(&mask) )
> >       {
> >           perfc_incr(need_flush_tlb_flush);
> > -        flush_tlb_mask(&mask);
> > +        flush_mask(&mask, FLUSH_TLB | FLUSH_HVM_ASID_CORE);
> 
> A rule of thumb is any modification in common code may impact Arm. This is a
> case here because the flag and the "new" function are not defined on Arm and
> therefore going to break the build.

flush_mask is not a new function, it's just not implemented on ARM I
guess.

> Why can't you keep flush_tlb_mask() here?

Because filtered_flush_tlb_mask is used in populate_physmap, and
changes to the phymap require an ASID flush on AMD hardware.

I will send an updated version.

Thanks, Roger.

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